Review: 3 Web stack monitors in the cloud

Monitoring services from Boundary, Circonus, and Librato combine simple setup and richly different capabilities

The simplest thing that Silverline does is report information about resources to their central server. It tracks basic numbers such as CPU load, network bandwidth, and disk bandwidth to help you get a handle on what the machines in your cluster are doing.

This is just the beginning -- Silverline also sneaks its way into the scheduling algorithms controlling the server. Once you put an application in a Silverline "container," Silverline can limit the resources it can consume, a process Librato calls "workload virtualization." Background tasks such as disk defragmentation can be given minimal headroom. High-computation tasks like converting photos or videos can also be limited so that a burst of uploads won't swamp your machines. You can control these spikes more easily at the OS level.

Librato Silverline monitors the essential metrics of the system. This graph shows the rise in network write.

This is, I think, a great idea. For a number of years, people have punted on all of the trouble with the OS configuration, instead setting up another virtual server running another copy of the OS. Every application was pushed off into its own virtual server even if this isolation wasn't required. This is largely a waste of OS copies, and it creates as many problems as it solves. Perhaps we can go back to one layer of the OS running directly on the iron without any virtualization sucking up CPU cycles.

The pricing of the Metrics service is set up like a taxi meter: You pay for every data item you store. Sending 50 measurements every minute costs $4.46 per month, for example. Librato provides an HTML5 calculator so that you can come up with your own measurements, but the rates seem to be entirely linear. Silverline is priced at $0.006 per CPU core hour. Librato's online calculator indicates that a month of virtual control over a single-core server would cost $4.38.

Turn on and tune in Setting up each of these monitoring services is surprisingly hassle-free. In some cases, I didn't have to do anything to my servers at all; I just added a URL into the Circonus or Librato service and waited for the tracking data to appear on my Web dashboard. In others, I contributed a bit of JavaScript to a Drupal Web page, a move that didn't require access to the files at all. Both Circonus and Librato offer these easy, nonintrusive setup options. This flexibility can be quite useful in a corporate world where installing new software might require a half-dozen meetings with skeptical system administrators who don't believe that anything is wrong with their machines.

Deploying monitoring as a service is also quite useful for navigating corporate politics. There are no data center czars citing every possible reason against setting up the new server. You just start paying by the hour; everything else is not your responsibility.

Of course there are worries too. Data about your site and its performance will be flowing into someone else's computers, and you'll probably never know where that data may end up. The monitoring service itself may not even know. This may be problematic if some of your customer data ends up in the log files being monitored. In most cases, the tools only capture information about speed and latency, but in other cases they even snarf SQL queries and the responses. The latest craze of embedding more and more parameters in URLs means that even lowly log files can hold sensitive info. These dangers can usually be avoided with care, but the potential for trouble remains.

Aside from these issues, the cloud-based monitoring tools are quite similar to the monitoring tools that we used to buy as software packages. They watch the network, ping the servers, download Web pages, and track the performance of URLs. If something seems wrong, they start sending emails or text messages. That's about it, but it may be all you need at 11 p.m.

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